1. Field of the Invention
The present invention relates to devices for driving documents, such as checks, perpendicularly in contact with a reference plane, during a process, such as printing or reading magnetic or optic information.
2. Discussion of the Related Art
FIG. 1 is a perspective view of a conventional device for processing documents. The device includes a frame 10 on which is mounted a driving device formed by a pair of rollers 72 and 14 in contact with each other and having parallel axes. One of the rollers, drive roller 12, is generally of a material having a high adherence to the documents. The drive roller is rotated by a motor (not shown). The other roller, idle roller 14, freely rotates about its axis. The frame 10 includes a reference plane 10-1 to which the roller axes are perpendicular and against which should be urged the lower edge of a document 16 driven by the device. In practice, this reference plane is the bottom of a groove 10-2 for guiding the document 16.
The documents to be driven arrive, inserted by hand or by another driving device, between the two rollers and are then dragged by adherence to the drive roller 12. The idle roller 14 provides sufficient pressure of the documents against the drive roller so that they are dragged.
In systems which process the documents, such as for printing or reading magnetic or optic information, the documents should have one of their edges in contact with a reference plane, which provides a reference for processing the documents. A processing device, designated 17, is represented in FIG. 1.
A first solution to ensure the contact with a reference plane is to provide the documents already in contact with the reference plane to the driving device and to construct the rollers (idle or drive roller) with an axis as perpendicular as possible to the reference plane 10-1. This solution requires a manufacturing accuracy that is particularly expensive.
Another solution is to tilt the axis of one of the rollers, generally the idle roller, in a plane parallel to the plane of the driven document 16. With such a solution, when the drive roller rotates in the "right" direction, the inclination of the idle roller urges the document towards the reference plane as it is driven. To limit the pressure applied to the document 16 once the latter is in contact with the reference plane 10-1, the idle roller is generally of a material having a low adherence. In contrast, if the drive roller rotates in the wrong direction, the driven documents are separated from the reference plane.
Thus, such a driving device which is inexpensive to manufacture is a unidirectional device.
European patent application 193,258 describes a device for driving documents having one edge in contact with a reference plane. The driving device includes a drive roller having its axis perpendicular to the reference plane and an idle roller pressing a driven document against the drive roller. The axis of the idle roller is freely tiltable in a plane parallel to the plane of the document, between two limit positions on either side of a position perpendicular to the reference plane.
A minimum resistance to rotation is provided between the idle roller and its axis, but the idle roller should be tiltable as freely as possible.
To reduce the resistance to tilting, the support of the idle roller is mounted to the frame through a ball-bearing. This mounting solution is particularly expensive and difficult to carry out, because the ball-bearing, which is very small, must be mounted with a high axial accuracy in order to ensure that the idle roller exerts sufficient pressure on the drive roller.